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对于订单式中小生产企业,物料供应是否及时以及生产进度是否按计划进行是影响订单交货期的关键因素。实际中,某些产品的物料价格随时间连续波动并具有规律性,而生产过程中由于插单多、工人流动性大、设备故障、质量返工等,生产完工期有一定的随机性。对于物料订购决策,传统方法主要考虑订单的投产日期以及物料采购成本最小化,而未考虑订单完工期的随机性特点。基于企业内部供应链集成及总成本最小化的系统思想,综合考虑物料价格的变化趋势以及随机生产完工期的统计规律,分别建立单一物料或多种物料订购情形下总生产成本(包括订购成本、制造成本、延迟完工或提早完工成本等)与订购日期的关系模型,并对其最优解进行讨论、分析与求解。当物料种类单一时,采用极值法对模型极小值点的存在性进行讨论;当物料种类较多时,构建了有约束条件的多决策变量非线性优化模型,并采用最优化理论中的拉格朗日乘子法(即PHR算法)进行求解。通过实例分析,得出的结论是物料最佳订购时间点与物料初始价格、价格波动周期、波动幅度、单位延迟或提早完工成本等因素相关。上述采购与生产集成的思想、模型构建的思路以及求解方法等可供有关人员参考。
For the order of small and medium-sized manufacturing enterprises, whether the timely supply of materials and production schedule as scheduled is the key factor affecting the delivery of the order. In fact, the material prices of some products fluctuate continuously and regularly with time. However, there is a certain degree of randomness in the production completion due to single insertion, large worker mobility, equipment failure and quality rework in the production process. For the material order decision, the traditional method mainly considers the production date of the order and the material purchase cost, but does not consider the random characteristic of the order completion period. Based on the system idea of minimizing the total supply chain cost and total cost in the enterprise, considering the trend of the material price and the statistical regularity of the completion of random production, the total production cost (including the ordering cost, Manufacturing costs, delays in completion or early completion of the cost, etc.) and the order date model, and its optimal solution to discuss, analyze and solve. When the type of material is single, the extremum method is used to discuss the existence of the minimum point of the model. When there are many kinds of materials, a nonlinear optimization model of multi-decision variables with constraints is constructed and the optimal model Grange multiplier method (ie, PHR algorithm) to solve. Through case analysis, the conclusion is that the best order time of materials is related to the initial price of materials, the period of price fluctuation, the fluctuation range, the unit delay or the cost of early completion. The above ideas of purchasing and production integration, the idea of how to build a model and the solution method are available for reference.